Method of producing gears



E. WILDHABER METHOD OF PRODUCING GEARS Dec. 27, 1927. 1,654,199

Filed Dec. 23, 1925 y 4\ Ernest WiZdhabez'mvEmoR l tofore proposed, a plurality of tools would Ill be required. The present method moreover is exact and theoretically correct.

The present invention relates particularly to a method in which a male tool is employed to out both members of a pair. It may be applied to the production of pairs of gears in which the profile of the teeth of the nongenerated member is straight or curved. This invention is particularly applicable to the production of curved tooth or spiral bevel and hypoid gears, but it will be under stood that it ma be employed also in the production of curved tooth spur gears or of other types of curved tooth gears.

For the purposes of illustration. the invein tion is described hereinafterin connection with the production of a pair of gears in which the tooth surfaces of the nongenerated member are spherical surfaces of revolution. Referring to the drawings:

In the methods heretofore proposed for cutting gears of the character stated. one tool was required for cutting the gear and another tool for cutting the pinion. This is illustrated in Figs. 2 and in which a gear cutter '10 and a pinion cutter 11 are shown by way of comparison. Both these tools may be rotarv annular face mills of the general character shown in Fig. 1 and pro vided with a plurality of cutting blades of circular profile. To produce the gear, the gear cutter 10 would be rotated on its axis in engagement with the blank, while the blank was held stationary. This would produce on the blank tooth surfaces which were surfaces of revolution whose profile was complementary to the profile of the cutting tool. In case the cutting tool was provided with blades of circular profile such as shown on the tool 10 the gear would have tooth surfaces which were spherical surfaces of revolution. A straight sided tool would produce a gear whose. tooth surfaces are conical surfaces of revolution. The pinion would be produced by rotating a toolsuch as shown at 11, whose cutting blades were of circular profile, if the tool used to produce the mate gear was of circular profile and of straight profile, if the tool used to produce the mate gear had a. straight cutting surface, in engagement with a blank, while the tool and blank were rolled relatively to each other in the manner of a gear meshing with the first gear. According to the methods heretofore proposed, the gear tool 10 would have cutting blades 12 provided with a circular cutting surface 13 on the outside whose radius of curvature 144.; was larger than the radius of curvature 15 of the inside circular cutting surface 16, and the pinion tool 11 would have cutting blades 17 provided with circular cutting surfaces 18 and 19, of which the cutting surface 18 has a smaller sphere radius 20 than the sphere radius 21. of the cutting surta e l9. and in which the snhere radius 2o would equal the sphere radius 15 of the gear cutter and the sphere radius 21 would equal the sphere. radius it of the gear cutter.

This method of producing a pair Hqlliicrl. therefore, a separate l'lOl for gear and pin ion. For cutting gears or pinions of dill'erent spiral or different dcdcndum angles, tools having cutting surfaces which were differently inclined to the cutter axis would he required. The difi'eren e in structure between tools required according to these heretofore proposed methods for cutting gears of different spiral or different dcdendum angles would be similar to the dill'ei'enee in structure between the tool required for cutting a gear or wheel and the tool required for cutting a pinion. save that usually, of course, the outside radius of the tool employed for cutting the gear is larger than its inside radiu Thus for cutting gears or pinions of one SJlltll and dedendum angle. the cutting blades might have the inclination to their axis 22 of the filll'i'lltfl' blades 11. of the tool 10. while for cutting gears or pinions of a different spiral or dedendnm angle. the cutting blades might have an inclination to their axis 23 such as have the cutting blades 17 of the tool 11.

lVith the present invention it is possible to use the same tool to out both members of a pair of gears and to use the same tool to cut various gears regardless of their spiral or dedendnm angles and the formation of their tooth surfaces. The present invention may be practised with a tool designed to cut theoretically accurate teeth, or with a tool H) constructed as to cut gears of romewhal modified tooth shape for the pui'l'riric ol' localizing bearing or making the gea s leer: sensitive to misalignment and small erro s in mounting.

For producing theoreti ally accurate gears, a tool such as shown in Figs. 1 and will, preferably, be utilised. This tool 2? is in the form of a rotary annular face mill provided 'ith a plurality of cutting blades 26 having cutting surfaces QT and .28 equal sphere radius 29 and ll) respe lii'elv whose sphere centers are at QT :nul 99 r spcctivelv on the axis ill of the tvol. 'lhis same tool or atool of identical on lrw'iic'ul can be used for cutting both members of n pair of gears of the character referred to and may be used for cutting various c:ii'. of different spiral and different de-zlendum angles. The method whcreb this lool may be employed to accomplish this result will be described now.

Referring to Figs. 7 and 9. l

. im ll'illlf gear blank having an ZlXls 32 and E indi-- cates a rotary cutter having an axis til. I15 indicates a. point midway of the length of a tooth such as might be produced by rolat vltl lllf llu

llo

lll

till

nee-4,199

ing the tool in engagement with the hlauli: Whiletlle same isheld stationary oir its auis, and 36 indicates line connecting the point 35 with the apex 32 ol the blank. In the methodeheretofore proposed. for cutting. the gear blank 31 by the process dcf-stzrihcih. and especially in those methods employing a male tool, the cutter was so positioned with relation to the blank that its axis 2-3 wasoltset from the axis t thebllank by an :u'uount equal to the product of the mean cutter radius 37 and the cosine ol' the upira l angle oil the teeth to he produced. on the hlanlt. So located. the cutter axis would he projected in Fig.1. 7 into the line l lo or into any line 38 which was at the same dietance fronrthe gear blank {lXlS the line 38. With the cutter position thusfixed, as required by the methods heretofore proposed. and assuming. as usual. equal pressure angles on hoth sides of the gear teeth the inclination of the cuttinr" edges or surfaces would he an already determined quantity. In other WOTCltS with the cutter position thus fixed. the location of the cphere centers 39 and 4:0 1.15;. 3} would he fixed and hence the structure ot the tool definitely determined. quent-ly, for cutting a gearot a en spiral or dedendlui'i angle, aspecial cutter had to be employed and this cutter could not he used to cut gears of other spiral or dedenduin angles.

lVith the present invention, a. standard cutter may be employed to out both: members of :1 pair of gears and various or re. This is accomplished by tilting the cutter to vary the inclination and otl'set of. its axis relative to the blunlt axis to suit the various: pears to he cut. This adjustment of the cutterto vary the inclination and otleet of its unis relative to the blank axle may he considered as tipping of the cutter axis 34; about the longitudinal tai'igent l1 oil the teeth to he produced on the gear. By tip-- ping the cutter axis about, this longitudinal tangent, the axis of the cutter may be inclined to any desired angle relative to the tooth surlaces to he cut, hence the cutter can be brought into any position suitable tor the predeteriniiuul standard. cutter.

The tipping: of the tool about this tangent ll does not actually have to he performed, ll the result desired occur-ed hy any other adjiietinent or adjustments of the tool, thi e iu sullicient. The important thing: is the tinal poeition ot the cutter;

My lnethod results in :11. slight cl'larure in the angle between the cutter axis and the hlanlt axie (Fig. 8) as computed with methods heretofore proposed. According to these latter methods. the angle between these two axes 34 and 3% is equal to 90 minus the root angle of the gear. the root angle being the angle between a plune tanduced upon the hlanlt; with the: pre. t

invention this offset 48 will he increased. Usually this otl set will he greater than the mean cutter i 'adiue.

With the present inventitm the tool: will he positioned asdescrihed for cutting a non {tonerated gear and the tool as usual will he rotated on its a; in engagement with the blank. while the blank itself held stationary.

IiLcuttinp; a pinion conjugate toa gear oi the .cha acter just described. that is, genera rated. prewiously proposed methods difi'er, According: to one method the offset of the pinion cutter from the axis of the treat it repreeents. that is, the gear on which the hlanh "e theoretically rolled to prodlict-i the .ueratod tooth profiles, is; the same as the offset of a tool when producing that gear. namely the product of the mean cu er radius and the cosine ol the spiral ant-21h). According to thisinethod the tool would he offset by a distance 46 (Fig. 9) from. the axis 32 of the {rear with Which theoretically the blank is rolled during]; cutting. In anothermethod. the axis of the pinion cutter 4:? When tu'olonged will intersect the axis e22 ot the gear.

In. producing? a pinion accordinolo this invention. the same principles are applied as laid. down HlDFWO tor iiroducruu the near. The cutter axis its inclined and from the hla ult axis so no to incline the cutting" hludes ol the tool to the desired angle relative to the tooth surface tolie prod need on the pin on. 'l h is is illustrated in Fi and it); \vllil tl ilflrugaiu iudicat 1 the oft theyzeur 3"! with whicl' i the blank is their rotically rolled. t) indicator; the cutter and. 51 its ax s. By illHjJlNlnQElle present invention to the produ: ion of the pinion. this tool 50 may be identical with the tool, fl used to produce the near. 'ln cutting the pinion. however, the oflset of the tool axis 51 from the gear axit-i 32 will be smaller than the offset 18 in cutting: the great and smaller thanthe product of the mean cutter radius and the cosine ol? the spiral angle ot the gear. The amount of the offset s indicated. ut- 52. This distance will always he difien out from zero and smaller than the ollsetd6 olithe tool according to known art. The inclination oi. the tool axis to the near axis "will depend upon the cone angle of the gear and the oil t ot the tool. In cutting the ill will be set in the manner just described and will be rotated on its axis in engagement with the blank .while'the tool and blank are rolled relatively to eachother in the manner of a gear meshing with its mate gear. The position of the pinion blank has not been shown in Figs. 9 and 10 for clearness. lVhen bevel gears are being cut the pinion axis will intersect the axis of the gear 3]. and when hypoid gears are being cut the pinion axis will be offset from the gear axis.

Having thus described my invention as applied to the production of theoretically accurate gears, that is, gears having mathematically mating tooth surfaces, it is only necessary to add a. few words with respect to the production of gears having a somewhat modified form of tooth. In many cases, especially if the gear and pinion mounting can not be made accurate enough or if the mounting is not rigid, it is desirable to produce tooth surfaces on gear and pinion which will permit of some relative adjustment of these members. In such cases a slight departure from theoretical tooth forms may be desirable. In such cases a tool similar to that shown in Fig. 3 may be employed, in which the radius of the outside spherical cutting surface is somewhat greater than the radius of the inside spherical cutting surface. The same tool, however, will be used for cutting both gear and pinion and the tool will be set with re lation to the gear for cutting gear and pin ion in the manner already described. This is in contradistinction to the methods heretofore proposed which would require two different cutters for producing the gear and pinion.

The modification of the cutter according to the manner just described will result in a tooth bearing which is in the center of the face, in an accurately mounted pair, and which gradually decreases toward the two ends of the teeth. The transverse profiles of the teeth will be of substantially the same'conformat-ion as those produced with tools such as shown at 25 in Figs. 1 and 2.

When it is desired to produce gears having tooth surfaces of somewhat modified profile from those produced by the tools 25, a cutter may be employed such as shown at 60 in Fig. 5 in which the cutting blades will be provided with cutting surfaces of differentsphere radii 61 and 62 respectively of which the sphere center 65 of the surface (33 *ill be located on one side of the cutter axis 64 and the sphere center 66 of the surface 67 will be located on the other side of the axis. In cutting a pair of gears with these modified profiles the same tool may be employed to produce both members of the pair.

According to my method, various gears may be produced with a small number of cutters of a desirable shape, whereas, here tofore, gears of the same character would have to be produced with special cutters, some of which, such as that shown in Fig. 4 would be of an undesirable structure. lVith my invention the process of cutting becomes standard and may be practised with the employment of a small number of tools.

A further advantage of this invention is that it permits of relieving the cutting blades of both gear and pinion tools in the direction of the cutter axis. as shown. This permits of relieving the blades in such way that the cutting profile is preserved al'tcr rc-- sharpening. This is a distinct advantage, for a pinion cutter, such as indicated in Fig. r as necessary with previous n'iethods of cutting, could only be relieved in a direction inclined to the cutter axis .23. as indicated by the arrow a. to provide proper cutting clearance. This necessary method of relieving the pinion tool I] would result in reducing the diameter of the cutting surfaces after shar].)ening so that the individual blades would have to be adjusted outwardly to restore the original cutting surface.

lVhile the present invention has been dcscribed particularly with reference to the production of gears with tools having circular cutting surfaces, it will be understood that it is capable of use with tools of difier cud curvature and with straight sided tools such as that shown in Fig. 6. The. tool 70 of Fig. (5 provided with an outside cutting surface 71. and an inside cutting surface 72 which will sweep out conical surfaces of revolution when the tool is rotated on its axis. This tool may be employed for cutting both gear and pinion and for cutting various gears or pinions by positioning it in the manner already described.

In cutting the non-generated member ac cording to this invention, it is preferable to finish both sides of a tooth space before in dexing, that is to cut the two sides simultaneously. here no cutter of proper point width is at hand, however, or where it is desired for any other reason, the gear may be cut one side at a time and the tool and blank reset to cut the other side. after one tooth side has been cut all the way around the gear. In cutting the pinion or the mate generated gear, I usually cut one side at a time, especially in the case. of hypoid gears. In doing so I preferably keep the angular setting y shown in Fig. l0 when cutting either side. It is to be uiulerstood. however, that it is possible to cut the pinion both sides simultaneously.

Both gear and. pinion will be cut tapering depth, that is, with the height of the teeth diminishing toward the apex. Preferably the gear and pinion will be cut so that all elements of their tooth surfaces intersect in the apex.

IVhile, preferably, a rotary annular tool lll such as; showz'1"will'beomployecl; it obvious tlmta plumfog tool may to [if-tell so s-a'et tlmt the axis about whloh it moves is inclined null otlsot in the manna]? (lo:

muborllmotrto of my in-mm-m, it will be outlaw-loud that the lmontion is CZtPfllJlQ f llll'lilll modification within the llnnto oil the disclosure and tho lpo ot' the tll lpfllltl dtl claims; and that this opplicutioi'l is intended 'Wltllm tho soopootthoappemlml claims.

l. The motlmt of protluoing" curved tootlr got .J Wl'l'icltcol'lsl ll llilfOltllJlHg a tool, hatlm ttll annular ou portion, in engwgw to tho lolaiolt that it: aw H up oil the bl" l; Ell'tflllltllllltfi g; or. the [mall radius: of the tool niuetllorl of procl'llclng curved. tooth gtrttttf llllltl; llil rotating-o tool hi1 ll'lg ttll*tlfnliltllttl cutting port-Howin alga with n, estlttionm'y goat loltlnlt, W11! mmlintz'lll'ling 'tllo tool so posltionocl rolzttlwely to tl1e-l3l2ti| that its EtXllSlfS :lnollnucl to the tltlilE of the blank; by on anglegretztot than 96 minus the root oingloof tho gear to ho produce-cl;

lnolinotl to of tho lalmllt by nmlntnl n" It): the tool to m to the blunt; tlmt its: Hk'lfil 0t 1 from tho pox of the lllitl'll'i' on :mnmnt grl ootor than tho 111mm roiling: oil? the tool :n'mlti liocl by tlto outline ol tllo Fllll'lll ol'lg lo n't' tlw: tooth to lJU pt'otlmeetl.

5. The llltlllllUtlU'f pl'oaloolmg wwoll tootll QULUH W lllill tfUllFlEvlt? to; roost mg :1 tool lmt lot on annular cutting; portion of oivculm :H'll pl'otlloin engugomont with a stationary" llg'tttl' lolonlg "While nmlntainlng the tool so positioned loltttivel y' to the HltWlllg lLllllrS detcrlbecl my invelltion What positioned rolntlvelj l'o the )l ink that lt: axis o'll'lot from the apart. ol the lJlzH'lliflll mmmt grentetthzm the In um rmllus of. the tool.

6. "llutmotlloll o'l' motlliol'ng oul'votl tooth To orm- 1 ol W in l'olmtiir :1 tool; lmw ing an 2 cutting; Hortlon of (:ixrdulm am 'nrolilo in on mont w ith Lt otzltlomujr 0m; ljllullt, wllile mullitzllmng the tool so [JUlilllOllGfly 'r'ellttl'voly to thoblrmlttlmt it: male; lrsoffset from the :1 pct; ol tl'lobla'tnlz, 1111 tlll'lilllllll router than the mama."radius: of *tl a toolqnultlplled]by tho cosinoot the spiral angleotthe gozuto be produced.

7. Thon'itthotl of protlucing' cur'votl toot gei'rswvlliolr consists in rotat 1g :1 toothltv mum mlal' cutting JUlllOll oil? circular plotlltvin-o gag lent with a Stationary gear blttnlt, Whllei ma-ilqtzlinlnggthe tool :alrmlt thitt i b K'lS lb -mclinetl to the axis oitthe blank by an angle greater. than 15111151 tho root in rotating M001; haw 311;; on 1111111112 11- ting portion; in eng; moot Wlllll'l u stattlomtry 1;" l 1 lt; "wlnlo ll'lllll'lfiitlllll'llg tl'lo tool to nos ltnlocl relatively to the blank that its axis lsollmot from the upon? ol" the lllanlt an amount tho motor radius of the tool the uoslnu 01' the ho lJlOCll-ilfifltl tlllll lltl relatively to tho blmlt that tho about which itntovuo M o tlXlr'fi moretlmn the moarnmrllum of tho tool.

111. The; method ol' pl'ocllmimg; g oom which oorltlistst-iz'r moving :wtool lll a omvoel path across the taco oil? :1 wtallolm gt blzmlt, while nlnlntzlinlng; tho tool to W xio'nml 15m relatively to the blank axis tlmt tl axis iltlJUllll WlllCl'l-lillO tool wows-2 it: otl'oet ll-om the bltmlt axis more than t [mama radius ol? the tool multiplied by tllt. vow-loo ot the spiral unglo ol the goal" to ho out.

lit The llllllllml ol pl'UtlllLll lf at pol:- ol um-vml tooth ljjltlll't; llllllll oozas' in limiting" one member ol the path. by ml. 1;}; it n'ljltoljjv tool in :t llllPl Qfil mtltml'oF-H tho foot ol :1 fill tl tlmllw l-goal lllillllt wllllo llllmintsllolng llllll 1:34

axis of said tool in definite offset relation to the axis of the blank, and in cutting the other member ofthe pair by moving an iden tical tool in a curved path across the face of the gear blank, while rolling the tool and blank relatively to each other in the manner of agear meshing with the mate gear while maintaining the axis of the tool offset from the axis of themate gear but by an amount less than itsoffset in. cutting such mate gear.

13. The method of producing a pair of curved tooth gears which consists in cutting each tooth surface of one member of the pair by moving a rotary tool in a curved path across the face of a stationary gear blank, while maintaining the axis of said tool in definite offset relation to the axis of the blank, and in cutting each tooth surface of the other member of the pair by moving a tool whose profile is of the same curvature as the tool employed in cutting the contacting tooth surface of the first gear in a curved pathacross the face of the gear blank, while rolling the tool and blankrelatively to each other in the manner of a gear meshing with the mate gear while maintaining the axis of the tool offset from the axis of the mate gear but by an amount less than its offset in cut ting such mate gear.

14. The method ofproducing a pair of curved tooth gears which consists in cutting one member of the pair by moving a rotary tool in a curved path across the face of a stationary gear blank, while maintaining said tool so positioned relative to the blank that its axis is offset from the axis of the blank more than the mean radius of the tool, and in cutting the other member of the pair by moving an identical tool in a curved path across the face of the gear blank while rolling the tool and blank relatively to each other in the manner of a gear meshing with the first gear and while maintaining the axis of the tool so positioned relatively to the axis of the gear with which the blank is rolling that it is offset from the axis of the first gear but by an amount less than its offset in cutting the first gear.

15. The method of producing one of a pair of curved tooth gears, of which one member is non-generated and the other memher is generated by a rolling motion of the tool and blank relatively to each other in the manner of a gear meshing with its mate gear, which consists in bodily adjusting a tool whose cutting edge has a definite inclination to the axis about which the tool moves, about a line tangent to a side of the tooth to be produced, until the cutting edge assumes the'desired inclination relative to the side of said tooth and imparting between tool and blank the required relative movement.

16. The method whereby different curved tooth gears of different tooth characteristics,

forming members of a pair of gears in which one member is non-generated and the other member is generated by a rolling motion of the cutting tool and blank relatively to each other in the manner of a gear meshing with its mate gear, may be produced with a rotary tool having an annular cutting portion whose effective cutting edge has a definite inclination to the tool axis which tourists in adjusting the tool in cutting each gear until its cutting edge has the desired inclination to the tooth surface to be produced on said gear and imparting between tool and blank the required relative movement.

17. The method of producing a pair of curved tooth gears which consists in producing one member of the pair by moving in a curved path across the face of a stationary gear blank a tool whose cutting edge has a definite inclination to the axis about which the tool moves, and in producing the other member of the pair by moving a tool, whose cutting edge moves on a circle of equal radius to that of the first cutting edge and has the same inclination to the axis about which it moves as the first tool, in a curved path across the face of the blank while rolling the tool and blank relatively to each other in the manner of a gear meshing with the first gear.

18. The method of producing a pair of longitudinally curved tooth gears which consists in cutting the side tooth surfaces of each gear with rotary annular face mills. corresponding cutting edges of which are located on the same radius and have the same inclination to the axes of the respective tools, by offsetting and inclining the axes of the respective tools from the respective blank axes to secure the desired spiral and dedendum angles on the blanks and to give the cutting edges of the tools the re quired inclinations lo the tooth sides to be cut to produce the desired pressure angles on the tooth sides of the blank.

19. The method of producing a pair of longitudinally curved tooth gears which consists in cutting the side tooth surfaces of one member of the pair by rotating an annular face mill in engagement with a tapered gear blank while maintaining the axis of the tool offset from the blank axis and inclined to the blank axis at an angle greater than minus the root angle of the blank, and in cutting the side tooth surfaces of the other member of the pair with a rotary annular face mill. the cutting edges of which are located on the same radius and have the same inclination to the tool axis as have corresponding cutting edges of the first tool, by offsetting and inclining the axis of the latter tool to the axis of the blank to be cut thereby to secure the desired spiral and dedendum angles on the blank and to give the cutting edges of the Ill) teel the required inclination to the tooth sides to be cut to produce the desired pree- SUIG angles of said tooth sides, and l'etziting staid tool in engagement with the blank n 'hile rotating); the bland: on its axis and sin1ultnneenely prodneing an additional relat ve movement between said tee]. and blank about an axis ei'lguhn'ly inclined to the blenl; axis.

20. The method, whereby longitudinally curved tooth genre with teeth of tapering depth may be cut with rotary annular face mills cei-i'es pending cutting edges of which we leeeted en the same radius and have the mine inclination to their respective teel zines, WlllCh consists in positioning the tool ei'npleyed relative to the blank to be cut, en that its axis is otlset from the blanlt axis and en inelined relative to the blank axis RS te pi'ednce the desired spiral and dedendmn angles: on the blank and its cutting edges are en inclined to the teeth sides to he cut as to prod L106 the deaiilked pressure englee en Hilltl teeth Sides.

ill. The method of cutting it longitinlinelly curved teeth gear having teeth of tapering depth, which eeneiste in cutting the tide teeth enrtzieee by positioning; it re try anniilzn' :l eee mill, so that its ziciie ie 0. i from the blflllh. min a distance dilt'erent from the mean entte radius and is inclined to the blank an. by an angle diil'erent from 90 mim'is the root angle of the blank; to be produced, and rotating said tool in engagement with the blank.

ERNEST WILDI-IABER. 

